A joint NIH -Tourette Syndrome Association Conference has emphasized the critical need for the testing and development of new pharmacotherapy for tic suppression in Tourette syndrome (TS). This submission is a safety, tolerability and efficacy pilot study using two medications that modulate glutamate neurotransmission, riluzole, a glutamate antagonist, and D-serine, a glutamate agonist. Glutamate is the primary excitatory neurotransmitter in the central nervous system, an essential component of pathways implicated in TS and an extensive modulator of dopamine, the major neurotransmitter associated with tics.